specifying 300 directories individually for indexing

I need to specify something on the order of 300 separate directories
for indexing among eventually 1,500, all at the same level in the
directory structure of my server. Since I can't pass a file of
directory names to SWISH-E, I need to use the IndexDir directive. This
leads me to question:
a) If the executable is in the directory above the directories I'm
indexing, can I not specify the full path? (e.g., "IndexDir 1235"
instead of " /full/path/to/the/directory/1235")
b) what is the upper limit in line size for a directive? (e.g.,
"IndexDir dir1 dir2 dir3 dir4....")
c) is there an upper limit on the number of IndexDir directives I can
have?
Thanks,
Roy